The metal additive manufacturing process creates a lot of heat in localised areas, due to the need to melt the powder using a laser. This can lead to stress points in the component when it cools. To reverse this, heat treatment is used to ‘normalise’ the material and put the grain structure into a uniform, relaxed state. Heat treatment can also optimise the properties of the component, adding features such as tensile strength or heat resistance.
Hot isostatic pressing (HIP) can also be used to reduce the porosity of metal parts. This process was originally developed for castings due to their higher porosity levels (up to 5% in some cases). Although laser powder bed fusion (L-PBF) produces much higher density parts (around 99.5% dense), the HIP process can also be used here to increase tensile and fatigue levels.